Hello
Is it because you are not the admin user and you don't know the other admin user's credential?
OR the computer doesnt have admin at all?
If the computer doesn't have admin at all, you can use this method to give yourself admin:
Hold down Shift key while you choose Windows restart, then go to Troubleshoot > Advanced Options > Startup Settings, click on restart, then choose option 4.
When prompted for password, leave it blank and enter.
When you are in safe mode, hold down windows + r keys, type in netplwiz and press enter.
Then double click on your username, go to Group Membership tab, make it admin.
Restart, log back into your user. You should now have admin access.
However, if the computer has admin, but you don't know the credential, then there's no way around this. Either you get the credential, or you have to backup the files and factory reset to start over.